Did a massive eruption spur Christianity in Iceland?

The 75-kilometer-long fissure that gave the Eldgjá “fire gorge” eruption its name is now a river valley in southern Iceland. Credit: Clive Oppenheimer.

The landscape and culture of Iceland, more so than any other country, have been shaped by volcanism. In a new study, researchers have refined the dates for the massive 10th-century Eldgjá eruption, which occurred just a few decades after the island was first settled. The findings may support a connection between the violent volcanism depicted in Iceland’s most celebrated medieval poem and the island’s conversion from paganism to Christianity.

The Eldgjá eruption originated under the Mýrdalsjökull Ice Cap on Katla Volcano in southern Iceland, and is estimated to have produced Iceland’s largest known lava floods, with more than 20 cubic kilometers of lava gushing out of a fissure more than 75 kilometers long. “This was a colossal eruption that went on episodically for many months and would have involved spectacular activity at the fissure, including fire fountains and explosions,” says Clive Oppenheimer, a volcanologist at Cambridge University in England and lead author of the new study, published in the journal Climatic Change. “It would have been very terrifying to witness.”

Iceland was settled in about 874, so people were living on the island — and quite possibly near Katla — at the time of the eruption. But despite Eldgjá’s massive size and widespread climatic impact, an exact date for the 10th-century event was not recorded. “This is pretty typical for eruptions in Iceland’s early recorded history. There are written records but the pagans didn’t keep track of years and record dates the same way we do,” says Thor Thordarson, a volcanologist at the University of Hawaii at Manoa, who was not involved in the new study.

In previous studies of sulfur deposited in ice cores by the eruption, researchers identified a 10-year window when the Eldgjá eruption could have taken place: sometime between 935 and 945. Oppenheimer and his colleagues took a new approach to narrowing this window, focusing on the section of a Greenland ice core that contained tephra and ash markers for both the 946 eruption of Changbaishan Volcano, on the border between China and North Korea, and the Eldgjá eruption.

“Ice core dating is not always exact, but the recently dated major eruption of Changbaishan — known as the Millennium Eruption — gave us an anchor for the Eldgjá event,” Oppenheimer says. The ice core record shows that the Eldgjá eruption started 7.5 years before the Millennium Eruption, pointing to its onset in the spring of 939. It persisted through the fall of 940. “This places the eruption squarely within the experience of the first two or three generations of Iceland’s settlers. Some of the first wave of migrants to Iceland, brought over as children, may well have witnessed the eruption,” he says.

Harsh winters and barren summers followed in the years after the Eldgjá eruption, due to the haze of sulfur that lingered in the atmosphere. “The effects of the Eldgjá eruption were likely devastating for people in Iceland, and the climatic effects of the sulfur emissions seem to have triggered famine in many parts of Europe, the Middle East and China in the years following the eruption,” Oppenheimer says.

The new study lends support to a connection previously suggested by experts in medieval literature that Eldgjá and its aftermath may have inspired Iceland’s most famous medieval poem, which dates to as early as 961: Völuspá — meaning “The Prophecy of the Seeress” — tells of a fiery end for Iceland’s pagan gods and the rise of a new singular god, a story scholars have long associated with the conversion of Iceland to Christianity around the turn of the 11th century. “In the poem, the god Odin consults a prophetess and she describes the whole history of the world from beginning to end, with the death of all the gods and giants. Interestingly, she describes this ending in terms of very vivid volcanic imagery,” Oppenheimer says.

Written in Old Norse-Icelandic, the poem describes a magnificent eruption with fireballs lighting up the sky and explosions heard for great distances. The poem also chronicles darkened skies and woeful summers following the event: “The sun starts to turn black, land sinks into sea; the bright stars scatter from the sky. Flame flickers up against the world-tree, fire flies high against heaven itself.”

“It’s interesting to think about how pagans and Christians in Iceland would have viewed this eruption and interpreted it in terms of their cosmologies and world views,” Oppenheimer says. “We can imagine that the eruption might have been rationalized by Christians as God’s retribution for the sins of the people.”

Still, the connections between the poem, volcanism and the conversion to Christianity remain speculative, Thordarson says. “This poem seems to be describing a volcanic eruption like Eldgjá, but my view is that a direct connection is a long shot. What I do accept is that Eldgjá and its fallout most likely ended the age of settlement in Iceland; it stopped people from coming to Iceland, since they couldn’t grow enough food to sustain the existing population,” he says. “Eldgjá had a huge impact on Iceland, there’s no question about that.”